Dual diaphragm vacuum servo

ABSTRACT

A vacuum servo construction having two flexible diaphragms in a single housing, with one connected to the other for a limited relative movement between the two, and the movement of one being modulated by changes in the vacuum levels. One of the diaphragms supports a carrier which houses the second diaphragm and, of which the following is a specification.

United States Patent Akman [451 May 2, 1972 541 DUAL DIAPHRAGM VACUUMSERVO 2,936,785 5/1960 Hastings ..92/49 3,090,359 5/1963 Hoppenstand...92/64 X [721 Dwbm" 3,385,275 5/1968 Burnia et a].... ...92/64 ux [73]Assignee; Ford Motor Company, Dearbom, Mich, 3,447,518 6/1969 Walker l23/1 17 A [22] Filed: 1970 Primary Examiner-Martin P. Schwadron [21]APP] N 7 9 Assistant Examiner-Irwin C. Cohen Attorney-John R. Faulknerand Robert E. McCollum [52] [1.8. CI ..92/49, 92/64 57 T T [51] Int. Cl..F0lb 19/02 [58] new 0 Search "HQ/48, 49 64; 123/ A vacuum servoconstruction having two flexible diaphragms in a single housing, withone connected to the other for a limited relative movement between thetwo and the moveg i [56] Re fences Cited ment of one being modulated bychanges in the vacuum levels. UNITED STATES PATENTS One of thediaphragms supports a carrier which houses the second diaphragm and, ofwhich the following is a specifica- 2,197,075 4/1940 Fitzgerald ..92/101 X on 2,465,714 3/1949 Elliott 2,849,864 9/1958 Hill et a1. ..92/49 X2 Claims, 2 Drawing Figures I 1-86 1 0 3O 1 I [g 92 I /4 g I: 72? s a2Patented May 2, 1972 INVENTOR 4/4/1457 I? AKA IAN BY ATTORNEYS DUALDIAPHRAGM VACUUM SERVO This invention relates, in general, to a fluidmotor construction. More specifically, it relates to a dual diaphragmvacuum motor assembly contained within a single housing.

This invention in particular is an improvement over the dual diaphragmfluid motor construction of Ser. No. 858,567, Frank M. Kittredge, filedSept. II, 1969. As stated in the latter application, anti-smogregulations relating to internal combustion engine exhaust emissioncontrols point out the desirability of selectively controlling theignition timing at all engine speed and load conditions not only toprovide minimum engine exhaust hydrocarbon and other undesirable exhaustemissions, but good engine performance and economy as well.

The dual diaphragm actuator of Ser. No. 858,567 provides, among otherthings, normal engine ignition advance timing as a function of changesin carburetor spark port vacuum during part throttle engine operation,as described. It does not, however, provide means for modulating theadvance as a function of engine load. This may be desirable at times tofurther control emissions, or for other reasons, such as perfonnance andeconomy.

This invention, therefore, provides a dual diaphragm fluid motorconstruction in which the ignition timing advance is capable of beingmodulated as a function of the change in engine load/vacuum, and thesecondary diaphragm is mounted to the primary diaphragm in a uniquemanner.

It is an object of the invention, therefore, to provide a dual diaphragmvacuum motor actuator in which the movement of the actuator isdetermined as a function of the changes in a plurality of sources ofvacuum operatively acting on the actua- I01.

It is another object of the invention to provide a dual diaphragm vacuumservo construction in which one of the diaphragms is secured to theother in a unique manner.

Other objects, features and advantages of the invention will 7 becomemore apparent upon reference to the succeeding detailed descriptionthereof, and to the drawings illustrating the preferred embodimentthereof, wherein;

FIG. I is a cross sectional view of a vacuum servo mechanism embodyingthe invention; and

FIG. 2 graphically illustrates a typical travel movement of one of theparts shown in FIG. 2 with changes in vacuum level.

Ser. No. 858,567 shows and describes an engine ignition timing system ofthe type in which the present invention could be used. However, it willbecome apparent that it will have many other uses wherever a servocontrol of the type to be described is desired. Therefore, only theservo control per se will be described;

In general, the vacuum motor assembly 10 shown in FIG. 1 includes twoflexible diaphragms l2 and 14 mounted in a housing 16 and definingseparate vacuum chambers 18 and 20 to provide various control movementsof an actuating rod 22. Chamber 20 is connected by a hose or line 24 toa first source of varying vacuum, such as, for example, the vacuum of anengine intake manifold. The other chamber 18 is connected by a hose orline 26 to a source of vacuum that alternates from essentially zerolevel to a maximum.

No controls are shown for varying the vacuum levels in chambers 18 and20 since they can be conventional, can be manually or automaticallyoperated, and the details and operation thereof are believed to beunnecessary for an understanding of the invention. Furthermore,reference may be had to Ser. No. 858,567 describing one such systemchanging the vacuum levels.

More specifically, vacuum motor 10 has an outer housing 16 that includesa sleeve portion 30, a central ring portion 32, and a torus-shapedportion 34, the latter having a central opening 36. The three portionsare held in the assembled position shown by an annular spring-like clamp38.

Sleeve portion 30 has a lip flange 40 around which is wrapped the outeredge 42 of the primary or first annular flexible diaphragm 12. Thelatter extends across the hollow space of housing 10, and is clamped ina sealing manner between ring 32 and lip flange 40, as shown. The end ofsleeve portion 30 is blocked by an adjustable plug 44, which togetherwith diaphragm l2 defines a first or primary vacuum chamber 18. Thelatter is connected by a bore or passage 48 to conduit 26 that containsany suitable source of vacuum that can be varied from essentially zeroor an atmospheric pressure level to a maximum.

Plug 44 seats one end of a spring 52 that biases diaphragm 12 to theright, as shown, for a purpose to be described. Plug 44 also acts as anadjustable stop to limit movement of diaphragm 12 in a leftwarddirection. Spring 52 is seated at its opposite end in a retainer 54riveted to a central portion of diaphragm 12.

Also riveted to the diaphragm is an annular, essentiallycrescent-shaped, carrier or support 56. The latter movably supports andmounts the secondary diaphragm 14, and together they define thesecondary vacuum chamber 20.

More specifically, carrier 56 includes an outer annular dish shaped part58 riveted to diaphragm 12, an inner flanged sleeve 60, and an annularclosure part 62. The latter is springclamped at its outer edge over theouter lip flange 64 of part 58, and has its inner edge located axiallyagainst a snap ring 66. Closure part 62 is formed with an annularprojecting portion 68 that abutts housing 16 at times to act as a stopfor movement of diaphragm 12 in one direction.

Secondary annular diaphragm 14 has a washer like shape, with its outeredge clamped between carrier parts 64 and 62. Its inner edge is wedgedaxially against flange 70 of sleeve 60 by a rubber O-ring 72.

A spring retainer 74 is riveted to one side of diaphragm 14, and seatsone end of a preloaded compression spring 76. Also riveted to a centralportion of the diaphragm is a disc 78 whose inner edge is staked at 80to the end of actuating rod 22. The disc is formed with an offset 82 toprovide an axial clearance space x" between the disc and flange 70, fora purpose to be described later. Rod 22 has an annular radial pro-'jection or abuttment 84 adapted to abutt or be abutted at times by theright end of the hub of sleeve 60. 7

Closure part 62 has an opening 86 that receives a hose fitting 88 havingan internal passage connected to an annular vacuum manifold 90. Thelatter is adapted to be connected by line 24 to any suitable source ofvacuum, such as engine intake manifold vacuum or sparkport vacuum, oralternating, for for example, that varies in level from zero oressentially atmospheric pressure to a maximum, much in the same manneras the vacuum in chamber 18.

To complete the construction, carrier outer part 58 is formed with apressure equalizing hole 92, as is disc 78 with hole 94, to provideatmospheric or ambient pressure conditions against the right and leftsides, respectively, of diaphragms 12 and 14. The ambient pressureconditions will exist by virtue of the annular clearance space betweenthe sleeve 60 and rod 22.

It will be clear that the preloads of primary and secondary springs 52and 76 can be chosen to suit the particular results desired, as will beexplained in connection with FIG. 2, for example. Also, the distance Xbetween disc 78 and sleeve flange 70 can be varied, as can the axialextent of stops 68 and 84. Also, changing the inclination of part 58 ofcarrier 56 will change the characteristics of operation of the servo.

FIG. 2 illustrates graphically typical changes in travel distance of rod22 for changes in vacuum level. Assume, for example, the vacuum level inchambers 18 and 20 initially is zero, or at atmospheric pressure. Theparts then will be positioned as shown. The preload of primary spring 52positions carrier 56 against the housing 16 and 68. The preload ofsecondary spring 76 nioves diaphragm 14 to the left and abutts stop 84against sleeve 60 to provide the maximum clearance X" between the sleeveand disc 78. Thus rod 22 has an initial position at O in FIG. 2.

Assume now that vacuum is applied only to chamber 18. Until the preloadof primary spring 52 is overcome, an increase in vacuum produces nomovement of rod 22. This is represented by the horizontal line A in FIG.2. Upon increase in vacuum, once the preload of spring 52 is overcome,diaphragm 12 then will begin moving to the left, as will carrier member56. Rod 22 likewise will move to the left under the influence of thesecondary spring 76 abutting flange 84 against sleeve 60. Thus, as thevacuum in the primary chamber increases, the rod 22 will moveprogressively between the points A and B in FIG. 2. Point B representsthe position of diaphragm 12 when the spring seat 54 has bottomedagainst the end of plug 44. Further increases in vacuum, therefore,produce no further leftward movement of the rod 22. This is representedby the horizontal line BC in FIG. 2.

Conversely, assume that there is no vacuum (atmospheric pressure) inchamber 18 and that we begin applying vacuum to chamber 20. Until thepreload of secondary spring 74 is overcome, rod 22 will remainstationary. Again, this is represented by the horizontal distance 0A inFIG. 2. As the vacuum increases above the preload of the spring,secondary diaphragm 14 will be drawn rightwardly to decrease thedistance X between the disc 78 and sleeve 60, which is bottomed againstthe housing portion 16. .This is represented by the line or curve AD inFIG. 2. Increasing vacuum will continue to move rod 22 to the rightuntil the disc 78 bottoms against the sleeve flange 70, at which timefurther movement of the rod 22 in the rightward direction will beprevented. This is represented by the point D on the curve in FIG. 2.From this point on, further increases in vacuum will not cause a furthertravel of rod 22. This is represented by the horizontal line DE.

Assume now, therefore, that vacuum is applied in a controlled manner toboth vacuum chambers 18 and 20 in a varying manner. It will be clearfrom a consideration of FIG. 2 that the two curves ABC and ADE will becombined because of the modulating action of the vacuum in the secondarychamber 20 on the action of the vacuum in primary chamber 18, and viceversa. Accordingly, assuming a vacuum existing in both chambers, ofdifferent values, until the preloads of the springs 52 and 76 areovercome, no travel of rod 22 in either direction will occur. Again thisis represented by the distance 0A in FIG. 2.

Now, with vacuum in both chambers, assume that. the vacuum level insecondary chamber 20 increases to where it overcomes the preload ofspring 76. If, at the same time, the vacuum in chamber 18 overcomes thepreload of spring 52, then vacuum in chamber 18 will be moving thecarrier 58 and sleeve 60 to the left at the same time that vacuum inchamber 20 is moving rod 22 to the right relative to carrier 58. Themodulating movement results in the dotted line curve AFG. AF representsthe rightward movement of rod 22 relative to sleeve 60, and FGrepresents the leftward movement of diaphragm l2 and carrier 58 and theresultant leftward movement of rod 22. Once the primary diaphragm 12 hasbottomed against plug 44, further leftward movement of rod 22 will beprevented. This is represented by line GH.

Thus, from the above, it will be seen that by varying the level ofvacuum in the secondary vacuum chamber in a selective manner as thevacuum varies in chamber 18, and/or varying the preloads of the primaryand secondary springs 52 and 76, and/or varying the spring rate ofsprings 52 and 76, and/or varying the axial distance X between disc 80and sleeve flange 70, and/or the other adjustable changes previouslydescribed, that the dotted line shown in FIG. 2 can be made to assume anumber of different shapes to provide a particular desired movement ofrod 22 in either or both directions.

From the above, therefore, it will be seen that the invention provides amovement of one diaphragm by vacuum in one direction modulated by theaction of vacuum in the secondary chamber, the modulating action varyingas a function of the selection of the spring rates and preloads andadjustable stop distances.

While the invention has been illustrated in its preferred embodiment inthe drawings, it will be clear to those skilled in the arts in which itpertains that many changes and modifications may be made thereto withoutdeparting from the scope of the invention.

I claim:

l. A fluid motor assembly comprising, a housing, first and secondflexible diaphragm members in said housing defining first and secondvacuum chambers, first and second means connecting said first and secondchambers to separate sources of fluid varying from a maximum essentiallyatmospheric pressure level to a minimum sub-atmospheric pressure'orvacuum level for reciprocable movement of said first and second membersas a function of the changes in vacuum acting thereon, first and secondspring means respectively biasing said first and second diaphragmmembers towards each other, movable actuating means connected to saidsecond diaphragm member for movement therewith, carrier means secured tosaid first member and extending adjacent said second member and saidhousing, means mounting said second diaphragm member on said carriermeans, said actuating member and said carrier means having a straddledinterengagement permitting a limited relative movement therebetween inopposite directions, said second spring means biasing said carrier meansand actuating members apart whereby movement of said first diaphragmmember upon application of vacuum to said first chamber moves said firstand second diaphragm members and actuating member in one direction, theapplication of vacuum to said second chamber modulating the movement ofsaid first diaphragm member by urging relative movement between saidcarrier means and said actuating member, said carrier means comprisingan annular hollow housing, said carrier means housing having radiallyspaced portions mounting the inner and outer edges of said seconddiaphragm member, said latter member having a washer-like shape, saidactuating member being axially movable within the inner portion of saidcarrier means housing and having axially spaced portions thereonextending radially on opposite sides of said carrier means inner housingportion to define stops for relative axial movement therebetween.

2. A fluid motor assembly comprising, a housing, first and secondflexible diaphragm members in said housing defining first and secondvacuum chambers, first and second means connecting said first and secondchambers to separate sources of fluid varying from a maximum essentiallyatmospheric pressure level to a minimum sub-atmospheric pressure orvacuum level for reciprocable movement of said first and second membersas a function of the changes in vacuum acting thereon, first and secondspring means respectively biasing said first and second diaphragmmembers towards each other, movable actuating means connected to saidsecond diaphragm member for movement therewith, carrier means secured tosaid first member and extending adjacent said second member and saidhousing, means mounting said second diaphragm member on said carriermeans, said actuating member and said carrier means having a straddledinterengagement permitting a limited relative movement therebetween inopposite directions, said second spring means biasing said carrier meansand actuating members apart whereby movement of said first diaphragmmember upon application of vacuum to said first chamber moves said firstand second diaphragm members and actuating member in one direction, theapplication of vacuum to said second chamber modulating the movement ofsaid first diaphragm member by urging relative movement between saidcarrier means and said actuating member, said carrier means comprising ahollow essentially crescent shaped support having an axially projectingportion engagable at times with said housing to stop movement of saidfirst diaphragm member in one direction, the said support having aninner sleeve portion, said means mounting said second diaphragm betweena radially outer portion of said support and said sleeve portion todefine said second chamber between said support and second diaphragm,said actuating member being secured to a radially median portion of saidsecond diaphragm permitting relative axial movement between one axialedge of said sleeve portion and said actuating member, and stop meansprojecting radially from said actuating member beyond the opposite edgeof said sleeve portion to limit relative axial movement between saidlatter member and sleeve portion.

1. A fluid motor assembly comprising, a housing, first and second flexible diaphragm members in said housing defining first and second vacuum chambers, first and second means connecting said first and second chambers to separate sources of fluid varying from a maximum essentially atmospheric pressure level to a minimum sub-atmospheric pressure or vacuum level for reciprocable movement of said first and second members as a function of the changes in vacuum acting thereon, first and second spring means respectively biasing said first and second diaphragm members towards each other, movable actuating means connected to said second diaphragm member for movement therewith, carrier means secured to said first member and extending adjacent said second member and said housing, means mounting said second diaphragm member on said carrier means, said actuating member and said carrier means having a straddled interengagement permitting a limited relative movement therebetween in opposite directions, said second spring means biasing said carrier means and actuating members apart whereby movement of said first diaphragm member upon application of vacuum to said first chamber moves said first and second diaphragm members and actuating member in one direction, the application of vacuum to said second chamber modulating the movement of said first diaphragm member by urging relative movement between said carrier means and said actuating member, said carrier means comprising an annular hollow housing, said carrier means housing having radially spaced portions mounting the inner and outer edges of said second diaphragm member, said latter member having a washer-like shape, said actuating member being axially movable within the inner portion of said carrier means housing and having axially spaced portions thereon extending radially on opposite sides of said carrier means inner housing portion to define stops for relative axial movement therebetween.
 2. A fluid motor assembly comprising, a housing, first and second flexible diaphragm members in said housing defining first and second vacuum chambers, first and second means connecting said first and second chambers to separate sources of fluid varying from a maximum essentially atmospheric pressure level to a minimum sub-atmospheric pressure or vacuum level for reciprocable movement of said first and second memBers as a function of the changes in vacuum acting thereon, first and second spring means respectively biasing said first and second diaphragm members towards each other, movable actuating means connected to said second diaphragm member for movement therewith, carrier means secured to said first member and extending adjacent said second member and said housing, means mounting said second diaphragm member on said carrier means, said actuating member and said carrier means having a straddled interengagement permitting a limited relative movement therebetween in opposite directions, said second spring means biasing said carrier means and actuating members apart whereby movement of said first diaphragm member upon application of vacuum to said first chamber moves said first and second diaphragm members and actuating member in one direction, the application of vacuum to said second chamber modulating the movement of said first diaphragm member by urging relative movement between said carrier means and said actuating member, said carrier means comprising a hollow essentially crescent shaped support having an axially projecting portion engagable at times with said housing to stop movement of said first diaphragm member in one direction, the said support having an inner sleeve portion, said means mounting said second diaphragm between a radially outer portion of said support and said sleeve portion to define said second chamber between said support and second diaphragm, said actuating member being secured to a radially median portion of said second diaphragm permitting relative axial movement between one axial edge of said sleeve portion and said actuating member, and stop means projecting radially from said actuating member beyond the opposite edge of said sleeve portion to limit relative axial movement between said latter member and sleeve portion. 